Adense group of bacteria that are difficult to treat with antibiotics is called a. a biofilm. b. parasitic. c. a plasmid conjugate. d. lysogenic.

A. A biofilm

Explanation:

Biofilms have high bacterial density near to 10000000 CFU/ml bacteria. Due to such high densities, these biofilms becomes resistant to the antibiotics. These biofilms are basically community of microorganisms which stick itself to some kind of surface be it living or non-living. The bacteria’s which get attached to these biofilm and grow in an environment in which they possess both tolerance and resistance towards any bactericidal agent. Due to this functional mechanism of bacterias with in the biofilm, they become resistant to antibiotics.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).

digestion

it excretes wastes